Certain clinical and morphologic findings are described in 54 necropsy patients aged 21-97 years (mean 64), 32 men (59%), with cardiac amyloid deposits extensive enough to cause fatal cardiac dysfunction. Chronic congestive heart failure (CHF) was present in 46 (85%). The duration of the CHF, known in 39 patients, ranged from 1-108 months (mean 18) and was for less than or equal to 12 months in 25 patients (64%). All 8 patients without CHF died suddenly and unexpectedly. Systematic arterial pressures were recorded in the last 3 months of life in 43 patients: the peak indirect systolic pressure was less than or equal to 130 mm H andthe diastolic less than 90 mm Hg in all. Electrocardiograms, recorded in the last 6 months of life in 40 patients, were abnormal in each: low voltage in 35 (63%); "myocardial infarction pattern" in 33 (83%); abnormal QRS axis in 29 (73%); arrhythmias in 29 (73%); first second or third degree heart block in 28 (45%), and complete bundle branch block in 7 (18%). In 30 patients, the QRS amplitude in all 12 leads was measured: in the 15 men it ranged from 60-197 mm (mean 99) (10 mm = 1m V) and in the 15 women, from 58-199 mm (mean 109). Diagnosis of amyloidosis was established by biopsy of non-cardiac organs or tissues during life in only 18 (33%) patients. During life the condition simulated hypertrophic cardiomyopathy in 5 patients, constrictive pericardial disease in 3 and coronary heart disease (because of angina pectoris) in 4.